CVE-2025-69224: AIOHTTP's Unicode processing of header values could cause parsing discrepancies

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-01-05 · updated 2026-10-11
Weakness: CWE-444

Description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Versions 3.13.2 and below of the Python HTTP parser may allow a request smuggling attack with the presence of non-ASCII characters. If a pure Python version of AIOHTTP is installed (i.e. without the usual C extensions) or AIOHTTP_NO_EXTENSIONS is enabled, then an attacker may be able to execute a request smuggling attack to bypass certain firewalls or proxy protections. This issue is fixed in version 3.13.3.

Affected products

aio-libs aiohttp: before 3.13.3 — fixed in 3.13.3
Pypi Aiohttp: before 3.13.3; 0.1, 0.10.0, 0.10.1, 0.10.2, 0.11.0, 0.12.0 (+297) — fixed in 3.13.3

How to fix

Upgrade to a fixed version: aio-libs aiohttp 3.13.3; Pypi Aiohttp 3.13.3. Check the vendor advisory for mitigations.

References

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